Field of the Invention
The invention relates to a method for producing nanofoam, and more particularly, to a method for producing polymer nanofoam.
Description of Related Art
Since the polymer foams have buffer characteristics, and structural characteristics thereof can generate the effect such as energy absorption or heat insulation, the polymer foam is often used as an insulating material.
Currently, a technique in which carbon dioxide is used to prepare a micro foaming material has been developed, and the technique can maintain material characteristics while reducing usage of the material. Such foaming technique produces foaming phenomenon by rapidly depressurizing a polymer in which gas is dissolved or rapidly increasing temperature at a high-pressure state. Microcellular foam can be generated via such a method, and it is believed that, in general, if a cell size less than 10 μm and a cell density greater than 109 cells/cm3 are satisfied, then such a foaming material can be referred to as microcellular foam.
With the development of nanotechnology, the possibility of preparing polymer nanofoams via a carbon dioxide foaming technique has also been explored in recent years. However, except for the difficulty of producing nanoscale cells, the main difficulty of above research includes increasing cell density from microscale (i.e. greater than 109 cells/cm3) to 1012 cells/cm3, even increasing to 1015-1016 cells/cm3.